When all the virtues run on the race course, only perseverance takes its reward.

Not found in the Christians are beginnings, but the end.

I agree, but 'quaerere' has to mean 'search forsomething' here.

Not searched for / seeked / looked for in the Christians are beginnings, but the end / goal.

So this would mean that if we compare all virtues, only perseverance lasts. And that's what the Christians are looking for. They don't care about the start, but are only interested in the result, the goal, the end. So Christians would be very intesested in perseverance.